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Common Beer Off Flavours – butterscotch, popcorn or butter.

Off Flavour: Diacetyl

Chemical Name: 2,3-butanedione

What to look for: Butter, oily, milky and feels a bit milky on the palate. This is quite easy to identify in a light lager but a darker beer, stout or ale at low levels  can be a desirable flavour.

When does it occur: Issues with oxygenation of your wort, short boils, low fermentation temps, racking to secondary too soon or a mutated yeast.

Will it disappear over time: No – the opposite occurs as diacetyl can increase over time. When alpha acetolactate breaks down especially with heat it forms greater concentrations.

Tips on how to avoid Diacetyl:

  • Make sure you complete a 60 minute vigorous boil.  Never cut this short.
  • Get as much oxygen into your wort prior to fermentation but avoid oxygen in your fermentation vessel once fermentation has commenced.
  • Increase the temperature at the end of fermentation for a couple of days.  This is called a diacetyl rest.  A couple of degrees is sufficient for the yeast to reabsorb that butteryness.
  • Yeast will continue to clean up your beer even after you think fermentation has finished.  Don’t rack and bottle your beer too soon. Ensure the little guys are done doing their work before you move your beer.

Other Common Off Flavours:

  1. Did someone fart in my beer?
  2. Who put a banana in my beer?
  3. Baby sick in my beer? Yuck
  4. I like hard rock but am not a Metal-Licker

 

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